The present invention relates to an ultrasonic diagnosis apparatus and in particular to a technique for measuring blood flow speed in a direction approximately perpendicular to an ultrasonic beam.
In the past, an ultrasonic pulse-Doppler method was put into practical use for measuring the speed of a moving part of a visceral organ such as a heart within a living body or a circulatory organ for blood or humor.
Only blood flow speed along the direction of an ultrasonic beam can be measured by using the conventional blood flow speed measuring system based on the Doppler method.
However, most of the blood vessels run in parallel with the body surface. When the blood flow speed is to be measured from the body surface, therefore, an ultrasonic probe must be tilted to align the beam direction with the blood vessel as much as possible. Accordingly, only the blood flow speed of extremely limited parts can be measured.
In general, blood flow speed is measured while the position of the blood vessel is being monitored on an ultrasonic tomographic (or cross-section) image. Although the ultrasonic tomographic image depicts the structual components located in a direction perpendicular to the beam with high resolution, it is extremely inferior in depicting the structual components located along the beam direction.
Accordingly, clear depiction of the flood vessel position in the ultrasonic tomographic image is contradictory to efficient measurement of the blood flow speed. This results in a problem of insufficient measurement of the blood flow speed of the flood vessels within the living body.